Process of making plaster board



Oct. 14 1924.

H. E. BROOKBY PROCESS OF MAKING PLASTER BOARD Filed Aug." 2Q. 1923 um hi1 INVENTOR. ARR) E. BROOKE) ATTORNEYS.

, To cilia/1012i it may concern:

, Plaster lioarihof which the following is a Patented Get. 14, 1924.

V currsn m HARRY E. BROOEBY, F EVANSTGN, ELLHKQIS.

Test

' 1,511,500 Price-e parent in PROCESS OF MAKING PLASTEB BOARD Application filed au ust 20, trees. Serial nol ceases.

specification,

This invention relates to improvements in building materials and more part cularly to 'a light weight wa-llboard or plaster board,

and is an improvement of the in'ventionset forth. in, my prior Patent No." 1,428,827, dated September 12-, 1922. i r

Fabricated plaster board for some time i has been used as a substitute for the customary wooden lath in buildings and plaster wallboard as a substitute for both wooden lath and plaster. I

The fabricated boards of this character formed of a plaster body protected by fibrous cover sheets when used as wallboard or a substitute for both lath and plaster are usually of a larger size than the'plastcr board or substitute for the lath alone and on account of the weight of the plaster body and increased size. usually 48 incheswide,

of an inch thiclrand from to 10 feet in length, are both cumbersome and heavy. It is an object of this invention to provide a light. weightbody for plaster wallboard with all the favorable characteristics and structural requirements of the present plaster wallboard but which will be easier to i handle in shipment and in application .upon

the building, wall or ceiling, and which while not detracting from the strength of the board will greatly reduce the cost of transportation.

With these and other objects in view, reference is had to the accompanying sheet of drawing which illustrates a preferred form of this invention, yet it is to be understood that minor detail changes may be made without departing from the scope thereof.

In the drawings:

Figure 1 is a view in side elevation, with parts broken away, of a form of a machine that may be used in the fabrication of the wallboard in accordance with this invention.

Figure 2 is a view in section of this improved wallboard illustrating the composition thereof.

The normal consistency of calcined gypthe fineness, metho sum varies in Water carrying capacity from cubic centimeters to 90 cubic centimeters per 100 grams of psum depending uponbf caloination and other factors known to the trade when calcmed gypsum is'produced, It has beendetermined that the same gypsum oa-n'be given an artificial consistency of 250 cubic centimeters, or more, of water carrying capacity to 100 grams of. gypsum by agitatingor rapidly stirring the gypsum in such an excess of water until the mixture is in a partly set condition. Gypsum so treated when set loses considerable strength due to loss in density, is very porous when the excess .water evaporates and'is much lighter in Weight, weighing approximately one third as much per cubic centimeter as the normal mixture of gypsum and water when set. Likewise it has been determined that while gypsum treated in the above manner will not bond to paper or the fibrous cover sheets "tor plaster wallboard, such gypsum will bond to paper coated with a gypsum and wav ter mixture of the. normal or low water carrying consistency; In producing w'allboard in accordance with this invention, same character of machine as illustrateddn my prior Patent 1,428,827, dated September 12, 1922, may be employed which is ofthe usual general construction as heretofore used in the manufacture of plaster wallboard and comprises a base 1 with spaced apart supports2supporting rolls of paper 3 of the proper width and character for the cover sheets 4 and 5 of the wallboard. An endless belt fipasses over rollers on the base which supports the bot tom cover sheet 4 between the supports2 and the encased board after it leaves the forming mechanism 7. The forming mechanism comprises means for turning over the edges of the lower cover sheet 4 to enclose the edges of the wallboard before the feeding of the upper cover sheet 5 thereover, all of which construction is well known in. this art.

Conveyors 7 and 8 are provided ad'acent each paper roll support 2 with a thir conveyor 9 interposed between them. These conveyors are all the same general construction and used in conveying a plastic mixand depositing the plastic mass upon the bottom cover sheet in the fabrication of plaster- I of ca ate conveyor deposits a plastic mass of gyp-' wallboard, however, in this case, the outer convelyors are utilized to deposit a thin layer cined gypsum 10 while the intermedisum and the desired excess of water agitated by rapidly moving stirring arms 13 upon the conveyor belt to form the light weight core 11. The three conveyors are spaced suflicient distances apart to allow suflicient set of the plastic bottom layer on the under cover sheet, of the core mixture and of the plastic upper layer thereon andallow for the spreading of each, preferably by spreading rolls 12, without interminglin the ingredients before the application the upper cover sheet. The remainder of the machine is re'ferably of the usual construction.

It is t 'erefore seen that by this; method a composition wallboard is formed which comprises a core 11 lighter in weight than calcined gypsum having a layer on each side that bonds thereto and to the cover sheets.

The agitating or rapidly stirring the calcined psum in a large excess of water to carry t e mixture partly into set causes the gypsum to take up approximately three times the normal amount of water as when mixed and allowed to set without agitation. The agitated mixture carrying the excess Water is less dense than the normal mixture and wheirset andthe excess water evaporated, an expanded, cellular, porous body of calcined gypsum is formed which on account of its construction is not only lighter but also of less structural strength than the normal set gy sum, however, as the cover sheets of we lboard impart the tensile strength to the board a core off this form of gypsum when bonded by a la er of normal calcined gypsum to the cover s eets produces a wallboard of the same tensile strength but lighter in weight than the normal gypsum wallboard.

The usual aggregates, such as sawdust, may be added before or during the mixing of the gypsum with the excess of water in the same manner as in forming plaster wallboard with the normal mixture of gypsum and water.

What I claim is:

1. A plaster wallboard comprising fibrous porous gypsum therebetween and bon ed.

thereto.

3. A plaster wallboard comprising fibrous cover sheets with layers of normal calcined psum bonded thereto and a core of expanded cellular gypsum therebetween.

4. A plaster wallboard comprising a core of expanded cellular calcined psum with a thin layer of normal calcin gypsum on each side bonded thereto and cover sheets bonded to the gypsum la ers.

5. The method of pr ucing composition wallboard comprising the provision of a cover sheet, depositing thereon a layer of plastic cemcntitious material adapted to bond thereto, depositing on such layer a core of the same material adapted to produce an' expanded cellular body and adapted to bond to said 1 layer, depositing upon the core a layer of the same material as the first and laying a second cover sheet over said last layer. a. 6. The method of producing plaster wallboard comprising the provision of a cover sheet, depositing a layer of plastic calcined gypsum thereon, depositing on such layer a core adapted to produce a li ht weight porous calcined gypsum body, fepositing upon the core a layer of lastic calcined gy sum and la ing a cover s eet upon said last ayer.

7. e method of producing plaster wallboard comprising the provision of a cover sheet, forming a thin layer of normal plastic calcined gypsum thereon, forming a core adapted to produce an expanded cellular calcined gypsum body thereon, forming a thin layer 0 normal plastic calcined gypsum on the core and providing a cover sheet upon 06 the last layer.

' HARRY E; BROOKBY. 

